EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA I 7^ 



Spirifer arenosus (Conrad) 



Plate 33, figures i-io 



For full description and figures see Palaentology of New York, 1859, 3: 425 pi. 98-100 ; v. 8, pt. 2, 1894, pi. 29, fig. 1-4; 

 pi. 30, fig. 3-7 



This well known and characteristic Oriskany species which occurs in 

 its best development in the sandy deposits of central New York is repre- 

 sented in the Grande Greve limestones by shells which occasionally attain 

 considerable dimensions. They are characteristic throughout, varying in 

 the degree of plication of fold and sinus and lateral slopes as do the typical 

 forms. They carry the flattened ribs with narrow interspaces and the very 

 fine radial lineation which is noted in N. Y. State Museum memoir 3 

 [p. 46] ' as a species character. Seldom in the Gaspe specimens is the 

 sinus deep or the fold high, nor does the large muscular scar of the ventral 

 valve make as conspicuous an effect on the internal cast as on the heavy 

 shelled forms of New York, but the latter is a feature dependent on gerontic 

 growth. The plications of the fold and sinus may at times be obscure but 

 this seems to be due largely to condition of retention. 



The shell is not among the commoner forms of Spirifer on the Forillon 

 but abounds at Perce. 



Localities. In division 2 at Grande Greve and Indian Cove and on 

 Dolbel brook at the base of the series. Much more abundant at Perce 

 Rock. 



Spirifer arenosus Conrad var. unicus Hall 



Plate 33, figure ii 



Spirifera unica Hall. Palaeontology of New York. 1865. 4: 203, pi. 30, fig. 21 

 Spirifer superb us Billings. Palaeozoic Fossils. 1874. v. 2, pt i, p. 45, pi. 3A, 



fig- 3, a, b 

 Spirifer billingsanus Schuchert. U. S. Geol. Sur. Bui. 87. 1897. p. 406 



Spirifera unica was described by Hall from a single ventral valve 

 derived from the Onondaga limestone of Erie county. It was characterized 

 by the sharp and angular deflection of the sinus, the relatively numerous 

 plications which are rounded or subangular rather than flattened by the 

 regularity of the plication on the sinus and the single median plication more 

 prominent than the rest. Professor Hall also noted the presence of fine 

 radial lines on the surface of the plications. 



Billings's single fine specimen ofS. superbus was so angulated on 

 the margin that it would stand upright when placed thereon. It was further 

 characterized by plications similar in form and number specially the stronger 



' In his description of S p. unicus [Pal. N. Y. 4: 204] Hall mentions not having 

 observed these fine lines in Sp. arenosus, but they are always present when the surface 

 is clearly retained. 



